A human vertebrae has a rearwardly projecting portion known as a spinous process. Bending of the spine can cause the spinous processes of adjacent vertebrae to be moved toward each other. This constricts the space in the spinal canal and foramina and, thus, may cause pain. Such constriction, which is known as stenosis, can be treated by the use of an implant in the space between adjacent spinous processes.
Some current implants are made of separate pieces which require insertion from opposite sides of the spine and in a posterior approach necessitate rather wide openings into a patient, cutting both left and right thoracolumbar fascia as well as stripping the multifidus muscles from their attachments. It is desirable to provide an implant for insertion between the spinous processes of adjacent vertebrae which can be inserted through a single opening in a minimal invasive approach and may be held firmly in position between the vertebrae.